1. Technical Field
The present invention relates to a test apparatus and a pin electronics card. More particularly, the present invention relates to a test apparatus that tests a device under test (DUT) such as a semiconductor circuit, and a pin electronics card for use in the test apparatus.
2. Related Art
Among test apparatuses that test DUTs such as semiconductor circuits, there is a known apparatus that includes a pin electronics card via which the apparatus exchanges signals with the DUT. The pin electronics card is provided between the main section of the test apparatus and the DUT to input a test signal from the test apparatus to the DUT and to receive an output signal from the DUT.
FIG. 4 shows an example configuration of a conventional pin electronics card 300. The pin electronics card 300 includes a driver 302, a comparator 304, an FET switch 312, a transmission path 314, and a reference voltage input section 316.
The driver 302 receives a test signal from the main section of the test apparatus and inputs it to a DUT. The driver 302 and the DUT are connected to each other via the FET switch 312 and the transmission path 314. The driver 302 includes a level selector switch 306, an enable switch 308, and an output resistor 310.
The comparator 304 receives an output signal from the DUT and compares the signal level of the output signal with a supplied reference voltage. The comparator 304 and the DUT are connected to each other via the FET switch 312 and the transmission path 314. The reference voltage input section 316 generates a predetermined reference voltage and inputs it to the comparator 304.
The FET switch 312 is switched on or off in response to a gate voltage given, and either connects the driver 302 and the comparator 304 to the DUT, or disconnects the driver 302 and the comparator 304 from the DUT. With this configuration, the main section of the test apparatus exchanges signals with the DUT. Presently, no relevant patent literature has been identified, so indication of any literature is provided.
The FET switch 312 in its ON state is represented by an equivalent circuit that includes: a resistor connected in series between the driver 302 and the DUT; and capacitive components between each terminal of the resistor and a ground potential. The equivalent circuit has a constant RC product, and cannot have both a low resistance and a low capacitance at the same time.
The FET switch 312 has a lower ON resistance when having a higher ON capacitance. In such a case, the FET switch 312 cannot allow a high-frequency signal to pass therethrough. Hence, tests using a high-frequency signal are impossible.
Therefore, for tests using a high-frequency signal to be possible, the ON resistance of the FET switch 312 may be increased. However, the comparator 304 is connected to the DUT via the FET switch 312. Hence, when the driver is enabled, the voltage comparison made by the comparator 304 is influenced by the ON resistance of the FET switch 312.
For example, the signal level of an output signal, which is to be input to the comparator 304, is voltage-divided between the output resistor 310 and the ON resistance of the FET switch 312. The larger the ON resistance of the FET switch 312 becomes, the larger the variation of the ON resistance becomes. Consequently, the voltage comparison accuracy of the comparator 304 is degraded.
Further, the ON resistance of the FET switch 312 changes in response to temperature, source-gate voltage, back-gate voltage, etc. Such changes are greater when the ON resistance of the FET switch 312 is larger. The voltage comparison accuracy of the comparator 304 would thus be further degraded.